Purpose:
The development of age-related macular degeneration (AMD) is thought to result from an accentuation of the aging process. A minimally invasive, high resolution imaging modality is vital to delineate the age-related structural abnormalities in the retina-choroid complex prior to apparent pathological manifestations of AMD. Based on the endogenous chromophores in the human retina-choroid complex, we employed two-photon excited autofuorescence (TPEF) imaging to characterize the morphological and spectral properties of the human photoreceptors, RPE and choriocapillaries ex vivo.
Methods:
The human retinas were obtained from four human Caucasian postmortem donor eyes (19, 55, 57 and 64 years old, with normal vision). TPEF imaging was performed with a customized multiphoton laser scanning microscope (Zeiss LSM 510) equipped with a femtosecond Ti:Sapphire laser (720-980 nm). The autofluorescence spectrum of RPE cells was measured with a confocal laser scanning microscope (Leica TCS SP2) coupled to a UV argon laser (364 nm).
Results:
As age increases, the regularity of the parafoveal photoreceptor mosaic appears to be preserved (Fig.a,b). Enlarged lipofuscin granules in the aged RPE demonstrate significantly blue-shifted autofluorescence (Fig.d), which coincides with the depletion of melanin pigments. Prominent fibrillar structures in elderly choriocapillaries may represent age-related structure and permeability alterations in the choroid (Fig.f).
Conclusions:
TPEF imaging is an elegant and highly efficient tool to delineate the thick, fragile and opaque retina-choroid complex. Requiring neither slicing nor labeling, the most vital components (photoreceptors, RPE, choriocapillaries, Bruch's membrane) in the human retina-choroid complex can be examined with high contrast and subcellular resolution, which may provide fresh insights into the pathogenesis of AMD.
Keywords: aging • retina • choroid